This invention relates generally to cooking appliances such as domestic ranges incorporating surface heating units, and more particularly to a detection arrangement for detecting that a surface unit is turned on with no cooking utensil in place on the surface unit. It is well known that users of electric ranges and cooktops waste electrical energy by reason of the fact that the user often does not immediately turn the control switch to OFF after removal of the cooking utensil from the heating element or may on occasion leave unattended a cooking utensil inadvertently placed on an element other than the one switched on. A number of prior art patents disclose means to detect either the presence or absence of a cooking utensil on a heating element and provide an arrangement for terminating electrical power for de-energizing the heating element in the event the cooking utensil is absent. Examples of such arrangements may be found in U.S. Pat. Nos. 4,214,150; 4,394,565; and 4,334,145. Each of these examples disclose detection arrangements involving mechanical switches activated by the placement of a utensil on the heating element, the state of the switch indicating, in effect, the presence or absence of a utensil from the heating element. Such devices work satisfactorily; however, the additional mechanical structure required by such devices significantly adds to the cost of manufacture of appliances incorporating such structures. It would be desirable to provide a pan removal detection arrangement which requires no additional mechanical structure.
It is therefore an object of the present invention to provide a pan removal detection arrangement for an electronically controlled cooking appliance of the type incorporating at least one automatic surface unit having a temperature sensor for power control purposes, which detection arrangement requires no additional mechanical structure but rather uses the temperature information derived from the temperature sensor in the automatic surface unit to detect the presence or absence of a utensil from the surface unit.
It is a further object of the present invention to provide a utensil removal detection arrangement of the foregoing type which upon detection automatically de-energizes the surface unit and provides a user discernible warning signal to alert the user of the occurrence of a utensil removal condition.